Re: TODO list for qemu+KVM networking performance v2

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Michael S. Tsirkin wrote:
> On Thu, Jun 04, 2009 at 01:16:05PM -0400, Gregory Haskins wrote:
>   
>> Michael S. Tsirkin wrote:
>>     
>>> As I'm new to qemu/kvm, to figure out how networking performance can be improved, I
>>> went over the code and took some notes.  As I did this, I tried to record ideas
>>> from recent discussions and ideas that came up on improving performance. Thus
>>> this list.
>>>
>>> This includes a partial overview of networking code in a virtual environment, with
>>> focus on performance: I'm only interested in sending and receiving packets,
>>> ignoring configuration etc.
>>>
>>> I have likely missed a ton of clever ideas and older discussions, and probably
>>> misunderstood some code. Please pipe up with corrections, additions, etc. And
>>> please don't take offence if I didn't attribute the idea correctly - most of
>>> them are marked mst by I don't claim they are original. Just let me know.
>>>
>>> And there are a couple of trivial questions on the code - I'll
>>> add answers here as they become available.
>>>
>>> I out up a copy at http://www.linux-kvm.org/page/Networking_Performance as
>>> well, and intend to dump updates there from time to time.
>>>   
>>>       
>> Hi Michael,
>>   Not sure if you have seen this, but I've already started to work on
>> the code for in-kernel devices and have a (currently non-virtio based)
>> proof-of-concept network device which you can for comparative data.  You
>> can find details here:
>>
>> http://lkml.org/lkml/2009/4/21/408
>>
>> <snip>
>>     
>
> Thanks
>
>   
>> (Will look at your list later, to see if I can add anything)
>>     
>>> ---
>>>
>>> Short term plans: I plan to start out with trying out the following ideas:
>>>
>>> save a copy in qemu on RX side in case of a single nic in vlan
>>> implement virtio-host kernel module
>>>
>>> *detail on virtio-host-net kernel module project*
>>>
>>> virtio-host-net is a simple character device which gets memory layout information
>>> from qemu, and uses this to convert between virtio descriptors to skbs.
>>> The skbs are then passed to/from raw socket (or we could bind virtio-host
>>> to physical device like raw socket does TBD).
>>>
>>> Interrupts will be reported to eventfd descriptors, and device will poll
>>> eventfd descriptors to get kicks from guest.
>>>
>>>   
>>>       
>> I currently have a virtio transport for vbus implemented, but it still
>> needs a virtio-net device-model backend written.
>>     
>
> You mean virtio-ring implementation?
>   

Right.

> I intended to basically start by reusing the code from
> Documentation/lguest/lguest.c
> Isn't this all there is to it?
>   

Not sure.  I reused the ring code already in the kernel.

>   
>>  If you are interested,
>> we can work on this together to implement your idea.  Its on my "todo"
>> list for vbus anyway, but I am currently distracted with the
>> irqfd/iosignalfd projects which are prereqs for vbus to be considered
>> for merge.
>>
>> Basically vbus is a framework for declaring in-kernel devices (not kvm
>> specific, per se) with a full security/containment model, a
>> hot-pluggable configuration engine, and a dynamically loadable 
>> device-model.  The framework takes care of the details of signal-path
>> and memory routing for you so that something like a virtio-net model can
>> be implemented once and work in a variety of environments such as kvm,
>> lguest, etc.
>>
>> Interested?
>> -Greg
>>
>>     
>
> It seems that a character device with a couple of ioctls would be simpler
> for an initial prototype.
>   

Suit yourself, but I suspect that by the time you build the prototype
you will either end up re-solving all the same problems anyway, or have
diminished functionality (or both).  Its actually very simple to declare
a new virtio-vbus device, but the choice is yours.  I can crank out a
skeleton for you, if you like.

-Greg


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